As radiation detectors for obtaining a radiograph of a subject, ones combining an image intensifier (hereinafter, referred to as “I.I.”) with a pickup tube or a solid-state image sensing device (e.g. a charge coupled device: hereinafter, referred to as “CCD”) have heretofore been used. These are configured to convert information on X rays transmitted through a subject into optical information, take this optical information into a television camera, and display it on a television monitor as an image or print it onto a film.
For these radiation detectors combining an I.I. with a pickup tube or a CCD, there has been a great need for the detection of smaller impaired parts and subtler lesions. As a new radiation detector to fulfill this need, a flat panel detector (hereinafter, referred to as “FPD”) making use of semiconductor techniques has been developed. This FPD is a semiconductor array formed in such a way that switching elements and capacitance formed on a glass substrate, for example is covered with a photoconductive film configured to convert radiation into charge. The FPD has features such as high resolution, light-weight and compact, and small image distortion.
As described, I.I.s and FPDs are available as detectors for obtaining a radiograph of a subject (see Japanese Patent Application Publication No. 2009-75951, for example).
As for the life of such a detector, the total accumulated amount of X-ray irradiation at the end of life is found when the detector is commercialized. By assuming the frequency of use of the detector, the durable term thereof is calculated. The user figures out the life of the detector on the basis of this durable term.
However, clinical settings in which an X-ray diagnostic apparatus equipped with the detector is installed differ from one another in terms of for what application and how frequently the apparatus is used. Thus, the assumed durable term mentioned above is inevitably inaccurate in practical use. Moreover, at present, no specific method has been established for notifying the operator of the end of life of the detector that is attributable to sensitivity deterioration by X-ray irradiation.